Background:
Vitamin D occurs in two forms: D2 (ergocalciferol) and D3 (cholecalciferol).Deficiency of vitamin D can lead to rickets in children, while in adults to osteoporosis, depression and multiple sclerosis. The aim of the pilot study was to analyze dietary supplementsin terms of the actual content of vitamin D3.

Material and methods:
The object of the study was ten random samples of dietary supplements from different manufacturers containing in their composition different values of vitamin D3. The manufacturers included a declaration on the content of vitamin D3 on the packaging. Theactual content of vitamin D3 was determined using high-performance liquid chromatography (HPLC). The content of vitamin D3 was determined based on a standard curve. Sigma Aldrich's Cholecalciferol standard was used.

Results:
In all the analyzed dietary supplements, the actual content of vitamin D is much lowerthan declared by the manufacturer. The carried-out tests revealed that the content of vitamin D3 in the analyzed supplements varied from 1.02 to 59.56 μg. In three cases borderline low valuesof vitamin D3 were noted. Furthermore, supplement 6 and 9 contained too low dosage of vitamin D3, to supplement a daily demand of an organism for this vitamin.

Conclusions:
Controlling the shortage of vitamin D in an organism decreases the risk of occurrence of civilization diseases. The results of pilot studies and other authors prove that this type of research should be continued in a wider scope on various food categories.